Derivatives of 2-amino-3-sulfopropionic acid

ABSTRACT

To obviate eutrophication of water, non-phosphorus detergent builders are provided. These are the water-soluble salts of 2-(N, N-di-(carboxymethyl))amino-3-sulfopropionic acid (e.g., the tetrasodium salt thereof). Conventional detergent actives may be used with these builders. Synthesis of the builders is described.

United States Patent [15] 3,683,014 Yang [451 Aug. 8, 1972 [54] DERIVATIVES OF 2-AMlNO-3- [56] References Cited [72] l 3 T| B t R L FOREIGN PATENTS 0R APPLICATIONS 626: "if" a M 456,312 5/1949 Canada ..260/5l3 N [73] Assignee: Ethyl Corporation, New York, NY. Primary Examiner Daniel D Horwitz [22] Filed: Oct. 14, 1970 Attorney-Donald L. Johnson [21] A 1. No.: 80 781 pp 57 ABSTRACT [52] US. Cl. ..260/513N To obviate eutrophication of water, non-phosphorus [51] Int. Cl ..C07c 143/12 detergent builders are provided. These are the water- [58] Field of Search ..260/5l3 N soluble salts of 2-[N,N-di-(carboxymethyl)]amino-3- sulfopropionic acid (e.g., the tetrasodium salt thereof). Conventional detergent actives may be used with these builders. Synthesis of the builders is described.

7Claims,NoDrawings BACKGROUND In the manufacture of detergent formulations for laundering and general purpose washing operations, it is common practice to employ detergent builders--si1bstances used in combination with surface-active compounds to aid in cleansing the articles being washed. The polyphosphates, notably sodium tripolyphosphate and tetrasodium pyrophosphate, are the commonly used detergent builders. However, these materials possess certain shortcomings. In the first place, the polyphosphates are susceptible to hydrolysis and degradation in aqueous solutions (Canadian Pat. No. 737,422). In addition, the phosphorus residues resulting from the widespread use of synthetic detergent formulations containing these phosphorus-containing builders have been said to contribute to eutrophication of rivers, lakes, underground streams, and other bodies of water. [Detergent Phosphorus Effect on Algae by Thomas E. Maloney, Journal of the Water Pollution Control Federation, Vol. 38, No. 1, pp. 38-45 (January 1966)].

To appreciate the magnitude of the problem, it has been estimated that over two billion pounds of salts of condensed phosphates are used in detergents each year in the United States. The phosphorus-containing builders can therefore be properly termed ubiquitous.

The desirability of providing an efficacious detergent THE INVENTION In accordance with this invention it has been found possible to reduce-indeed, eliminatethe phosphorus-containing builders in detergent formulations without sacrifice of cleaning power and brightness of employing as a detergent builder a water-soluble salt of 2[N,N-di-(carboxymethyl)]amino-3-sulfopropionic acid. This acid has the formula:

CH2SO3H N CHzC 0 0 H 2 The preferred salts are the alkali metal salts with potassium and especially sodium being particularly preferred. Other suitable salts include the ammonium and substituted ammonium salts.

An embodiment of this invention involves providing as new compounds, 2-[N,N-di-(carboxymethyl)] amino-3-sulfopropionic acid and its water-soluble salts, those of sodium and potassium being preferred. Another embodiment is a process for producing them.

The builders of this invention may be prepared by reacting an alkali metal salt of 2-amino-3-sulfopropionic acid with an alkali metal salt of a monohaloacetic acid in an alkaline aqueous system:

CHQSOZM CHCOOM ZXCHzCOOM 2MOH lei.

CI'I2S03M CHCOOM ZMX N(CH2COOM)2 (M is preferably Na of K; X is preferably, Cl Br, or I). For best results, the reaction is conducted at mildly elevated temperatures (e.g., 60-90 C., preferably 75 C.) using an alkali metal hydroxide in amount sufficient to keep the reaction solution alkaline but insufficient to cause the pH to exceed 10. Treatment of the resultant organic acid salt with mineral acid (e.g., HCl) or acidic ion-exchange resin liberates the free acid.

The builders of this invention can be advantageously used with a wide variety of detergent actives or surfactants, including those known in the art as anionic, cationic, nonionic, ampholytic, and Zwitterionic detergents as well as any suitable mixture of such detergents. When the resultant washing compositions are used in aqueous washing systems, the cleaning power of the formulation is enhanced in much the same way as when the commonly used polyphosphate builders are employed. Yet the present builder systems are more resistant to hydrolytic degradation that the polyphosphates and do not contribute to the eutrophication problems characteristic of phosphorus-containing builders.

Accordingly, this invention provides, inter alia, a washing composition composed of an organic detergent surfactant suitable for use in water and, as a builder, a water-soluble salt of 2-[N,N-di-(carboxymethyl)]amino-3-sulfopropionic acid. Although the proportions may be varied to suit the needs of the occasion, the weight ratio of the detergent surfactant to the builder of this invention will normally fall within the range of about 1:10 to about 3:1. The preferred ratios are within the range of about 1:5 to about 3:2.

As noted above, the builder of this invention is generally employed in the form of a water-soluble salt, notably an alkali metal salt, an ammonium salt, or an alkyl anunonium salt. The alkali metal salts can involve one or a mixture of alkali metal salts although the potassium or sodium salts, especially the tetrasodium salt of 2-[N,N-di-(carboxymethyl)]amino-3-sulfopropionic acid, are preferred because of their relatively low cost and enhanced effectiveness. Because the detergent formulations are generally used in alkaline aqueous systems, it is entirely feasible to use in their manufacture either 2-[N,N-di-(carboxymethyl)] amino-3-sulfopropionic acid itself or the partially neutralized free acid. The free acid group(s) will be converted to the appropriate salt at least as soon as the formulations are put to use in an alkaline environment.

IOIOAR n11:

For best results, the formulations of this invention will provide in aqueous solution a pH between about 8 and about 12.

As noted above, the builders of this invention can be used with a wide variety of detergents including those classed in the art as anionic detergents, cationic detergents, nonionic detergents, ampholytic (i.e., amphoteric) detergents, and Zwitterionic detergents, and any suitable mixture of two or more of these (whether from the same class or from different classes). The anionic surface-active compounds are generally described as compounds which contain hydrophilic and lyophilic groups in their molecular structure and which ionize in an aqueous medium to give anions containing the lyophilic group. Typical of these compounds are the alkali metal salts of organic sulfonates or sulfates, such as the alkali metal alkyl aryl sulfonates and the alkali metal salts of sulfates of straight chain primary alcohols. Sodium dodecylbenzene sulfonate and sodium lauryl sulfate are typical examples of these anionic surface-active compounds (anionic synthetic detergents). For a further amplification or anionic organic detergents which can be successfully built in accordance with this invention, reference should be had to U.S. Pat. No. 3,422,021, particularly the passage extending from Column 1 1, line 47 through Column 12, line l5,inc1uding the references therein cited, which passage is incorporated herein as if fully set out in this specification.

The cationic detergents are those which ionize in an aqueous medium to give cations containing the lyophilic group. Typical of these compounds are the quatemary ammonium salts which contain an alkyl group of about 12 to about 18 carbon atoms, such as lauryl benzyl dimethyl ammonium chloride. Compounds of this nature are used in detergent formulations for special purposes, e.g., sanitizing and fabric softening.

Nonionic surface-active compounds are generally described as compounds which do not ionize in water solution. Oftentimes these possess hydrophilic characteristics by virtue of the presence therein of an oxygenated chain (e.g., a polyoxyethylene chain), the lyophilic portion of the molecule being derived from fatty acids, phenols, alcohols, amides or amines. Exemplary materials are the poly-( ethylene oxide) condensates of alkyl phenols (e.g., the condensation product formed from one mole of nonyl phenol and ten moles of ethylene oxide), and the condensation products of aliphatic alcohols and ethylene oxide (e.g., the condensation product formed from 1 mole of tridecanol and 12 moles of ethylene oxide). Reference should be had to US. Pat. No. 3,422,021, especially the passage extending from Column 12, line 16 through Column 13, line 26 where a fairly extensive discussion and exempliflcation of nonionic synthetic detergents is set forth. Inasmuch as the nonionic synthetic detergents set forth in that passage can be successfully built in accordance with this invention, the foregoing passage is incorporated herein as if fully set out in this specification.

The ampholytic surfactants are compounds having both anionic and cationic groups in the same molecule. Exemplary of such materials are derivatives of aliphatic amines which contain a long chain of about eight to about 18 carbon atoms and an anionic water solubilizing group, e.g., carboxysulfo, sulfo or sulfato. Examples of ampholytic detergents are sodium-3- dodecylaminopropionate, sodium-3- dodecylaminopropane sulfonate, sodium N-methyl taurate, and related substances such as higher alkyl disubstituted amino acids, betaines, thetines, sulfated long chain olefinic amines, and sulfated imidazoline derivatives.

Zwitterionic synthetic detergents are generally regarded as derivatives of aliphatic quarternary ammonium compounds, in which the aliphatic radical may be straight chain or branched and wherein one of the aliphatic substituents contains from about eight to 18 carbon atoms and one contains an anionic water solubilizing group, e.g., carboxy, sulfo, or sulfato. Examples of compounds falling within this definition are 3-( N ,N- dimethyl-N-hexadecylammonio )-propanel -sulfonate and 3-N,N-dimethyl-N-hexadecylammonio-Z-hydroxypropane-l-sulfonate. For a still further appreciation of surface-active compounds (synthetic detergents) which can be employed in the practice of this invention reference may be had, for example, to the disclosures of US. Pat. No. 2,961,409 and French Pat. No. 1,398,753.

The detergent builders of this invention have been found to perform exceedingly well with anionic surface-active compounds and therefore this constitutes a preferred embodiment of the invention.

Another preferred embodiment of this invention is a washing composition comprising an organic detergent surfactant, a water-soluble monovalent salt of 2-[N,N- di-(carboxymethyl)]amino-3-sulfopropionic acid as a builder, and about 2 to about 10 percent by weight based on the total weight of the composition of a watersoluble alkali metal silicate. The cleaning efficacy of these preferred compositions is at least comparable to commercially available household and laundry formulations. Moreover, the soluble silicates of such alkali metals as sodium and potassium serve as effective corrosion inhibitors. In accordance with this preferred embodiment it is desirable to employ one or more silicates of sodium or potassium, or both, wherein the weight ratio of SiO2:M O (M=Na or K) is in the range offrom about 1:1 to about 2.8: 1. Sodium silicates wherein this ratio is in the range of about 1.611 to about 2.5:1 are especially useful because of their low cost and effectiveness.

Another preferred embodiment of this invention involves including with the mixture of the organic detergent surfactant and the 2-[N,N-di-(carboxymethyl)1 amino3-sulfopropionic acid builder (e.g., the tetrasodium salt, the tetrapotassium salt, or the mixed sodium-potassium salts thereof) an alkali metal sulfate, preferably sodium sulfate, or an alkali metal carbonate, preferably sodium carbonate, or both. Amounts up to about 60 percent by weight of the total formulation are suitable. These formulations are effective, economical mainstays of finished detergent formulations for laundry, household and/or industrial use. In the preferred compositions the amount of alkali metal sulfate and/or alkali metal carbonate is generally from about 10 to about 50 percent by weight based on the total weight of the formulation.

Finished detergent formulations of this invention may contain minor amounts of other commonly used materials in order to enhance the effectiveness or at tractiveness of the product. Exemplary of such materials are soluble sodium carboxymethyl cellulose or other soil redeposition inhibitors; benzotriazole, ethylene thiourea, or other tarnish inhibitors; perfume; fluorescers; dyes or pigments; brightening agents; enzymes; water; alcohols; other builder additives, such as the water-soluble salts of ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, nitrilotriacetic acid and N-(2-hydroxyethyl)- nitrilodiacetic acid; and pH adjusters, such as sodium hydroxide and potassium hydroxide. In the built liquid detergent formulations of this invention, the use of hydrotropic agents may be found efficacious. Suitable hydrotropes include the water-soluble alkali metal salts of toluene sulfonic acid, benzene sulfonic acid, and xylene sulfonic acid. Potassium toluene sulfonate and sodium toluene sulfonate are preferred for this use and will normally be employed in concentrates ranging up to about or 12 percent by weight based on the total composition. a

It will be apparent from the foregoing that the compositions of this invention may be formulated according to any of the various commercially desirable forms. For example, the formulations of this invention may be provided in granular form, in liquid form, in tablet form, or in the form of flakes or powders.

The relative proportions and absolute quantities of the several ingredients of the finished compositions of this invention are susceptible to variation and in most cases will vary depending upon such factors as the nature of the particular ingredients being utilized, the end use of which the composition is intended to be put, the relative costs of the ingredients, and the like. For example, the total concentration of the detergent formulations of this invention in water will normally range below about 0.3 percent by weight although it is entirely feasible to utilize higher concentrations where the circumstances warrant or justify the use of higher concentrations. In most cases the aqueous washing solutions of this invention will contain from about 0.05 to about 0.25 weight percent of combined detergent active(s) and builder. The preferred compositions of this invention are phosphorus-free although it may be desired to include therein reduced quantities of conventional phosphorus-containing materials such as sodium tripolyphosphate, tetrasodium pyrophosphate, salts of substituted methylene diphosphonic acids, long chain tertiary phosphine oxides, or the like.

The invention is not to be limited to any particular method of mixing the builder and the detergent. The builder may be mechanically mixed in, crutched in the detergent in the form of a slurry, or dissolved in a solution of the detergent. In addition, the builder system may be admixed with the detergent in any of the forms in which the detergent is manufactured, as well as being added simultaneously or separately to an aqueous solution. In any event, the present builder system is intended to be used with the detergent at the time of application as a cleansing agent.

In order to still further illustrate the practice of this invention, the following examples are presented.

EXAMPLE I L-2-amino-3-sulfopropionic acid, 17 grams (0.1 mole), was dissolved in 100 ml. of water and was neutralized with 8 grams of NaOH dissolved in 50 ml.

of water. The salt solution and 24 grams of ClCH COONa were placed in a 500 ml. three-necked flask equipped with a mechanical stirrer, a combination pH electrode and a dropping funnel. With the temperature of the mixture maintained at 75 C., 8 grams of NaOl-I in 50 ml. of water was added dropwise such that the pH of the mixture did not exceed 10. The first half of the alkali solution was taken up rather readily whereas the addition of the second half consumed more than a day. The mixture was left stirred for 24' more hours.

The reaction mixture was concentrated to about ml. at 70 C. and was divided into three equal portions. Each portion was passed through a 2.5 X 100 cm. column of an ion-exchange resin (Dowex 50 W-Xl, 50/ 100 mesh) which had been pretreated with 300 ml. of 10 percent HCl and washed until chloride-free. Water was used as the eluent. The effluents with pH 1 were collected, combined and evaporated to dryness at 50 C. The residue was recrystallized from water to yield 14 grams of colorless solid after drying. It melted with decomposition at 200 C. The NMR and IR spectra verified its structure. The NMR spectra taken in both dimethyl sulfoxide and D 0 showed it to contain two moles of water of hydration per molecule of 2- [N,N-di-(carboxymethyl)]-amino-3-sulfopropionic acid.

EXAMPLE II A preferred built formulation of this invention had the following composition:

Weight Percent Dodecylbenzene sulfonate (a typical linear alkyl benzene sulfonate) 20.0 Sodium silicate (ratio SiO,:Na O of 2.4: l) 6.0 Sodium carboxymethyl cellulose 0.6 Sodium sulfate 33.4 Tetrasodium salt of 2-[N,N-di- (carboxymethyl)lamino-3-sulfopropionic acid 40.0

The performance of this, detergent composition was evaluated by use of the standard Launder-Ometer test. In particular, the formulation was dissolved in water to a concentration of 0.15 weight percent and the pH of the solution adjusted to 9.5 with small amounts of sodium hydroxide solution. The water had a hardness of 150 ppm (Ca/Mg 3/2). Swatches of standard artificially soiled cloth were subjected to the washing procedure. The Launder-Ometer bath temperature was fixed at F. and the washing span was 10 minutes. After washing, the samples were removed from the washing solution and thoroughly rinsed with pure water. After drying, the whiteness of the cloths was ascertained by use of a standard commercially available reflectance photometer. The identical procedure also was employed with a formulation identical to that described above with the exception that sodium tripolyphosphate was used in lieu of the tetrasodium salt of 2-[N,N-di- (carboxymethyl ]amino-3-sulfopropionic acid.

In these tests it was established that the formulation of this invention was essentially as effective as the corresponding sodium tripolyphosphate formulation. In particular, the cloths washed with the formulation of this invention had a whiteness of 95 as compared to the whiteness of the same kind of soiled cloths washed in EXAMPLE Ill Some illustrative solid heavy duty laundering formulations of this invention are as follows (percentages being weight percentages):

Surface-active agent (See Note 1) l25% Tetrasodium salt of 2-[N,N-di- (carboxymethyl)]amino-3-sulfopropionic acid l0-25% Sodium metasilicate (anhydrous) 2-l0% Sodium carboxymethyl cellulose 1% Optical brightener (fluorescent dye) 0.1% Perfume 01% Sodium sulfate (See Note 2) Balance to l00% EXAMPLE IV Typical liquid laundering formulations of this invention are as follows (percentages being weight percentages):

Surface-active agent (See Note 1 above) l0-l5% Tetrasodium salt of 2-[N,N-di- (carboxymethyl)lamino-3-sulfopropionic acid (See Note 3) l0-20% Potassium metasilicate 2l0% Sodium carboxymethyl cellulose 1% Sodium benzene sulfonate (See Note 4) 5-l0% Optical brightener (fluorescent dye) 0 l% Water Balance to 100% The tetrasodium salt of 2-[N,N-di-(carboxymethyl)]amino-3-sul' fopropionic acid may be totally or partially replaced by the tetrapotassium salt of 2-[N,N-di-(carboxymethyl)]-amino-3-sulfopropionic acid. The sodium benzene sulfonate may be totally or partially replaced by potassium benzene sulfonate, sodium toluene sulfonate, sodium xylene sulfonate, etc.

it is not intended that this invention be unduly limited by the exemplifications herein provided.

Besides being effective detergent builders, 2-[N,N- di-(carboxymethyl) ]amino-3-sulfopropionic acid and its water-soluble salts are highly effective sequesterants for calcium in aqueous systems.

I claim:

1. A compound selected from the group consisting of 2-[N,N-di-(carboxymethyl) ]amino-3-sulfopropionic acid and the water-soluble salts thereof.

2. The free acid of claim 1.

3. A salt according to claim 1 characterized in that it is an alkali metal salt of said acid.

4. A salt according to claim 1 characterized in that it is the tetrasodium salt of said acid.

5. A process for the preparation of alkali metal salts of 2-[N,N-di-(carboxymethyl) ]amino-3-sulfopropionic acid which comprises reacting an alkali metal salt of 2-amino-3-sulfopropionic acid with an alkali metal salt of a monohaloacetic acid in an alkaline aqueous system at a mildly elevated temperature and at a pH not in excess of 10.

6. The process of claim 5 wherein the alkali metal 22 itt tsaga a mat a'c as sa it aaaa; bromine or iodine.

7. The process of claim 5 wherein the alkali metal content of said system is sodium, the halogen of the haloacetic acid is chlorine, and the temperature is kept in the vicinity of about -75 C.

(5/69) UNITEsTATEs PATENT UFFICE CERTIFICATE OF C9 EUHN Patent No. 5, 683, O11L Dated August 8 L 1972 Inventor( s) Meiling T. Yang It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 1, between lines 6 and 7, insert C-ross Reference to Related Application This application is a. division of Application Serial No. 825, 985, filed May 19, 1969, which has since issued 'as U.S. 3,655,829.

Signed and sealed this 9th day of January 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissioner of Patents 

2. The free acid of claim
 1. 3. A salt according to claim 1 characterized in that it is an alkali metal salt of said acid.
 4. A salt according to claim 1 characterized in that it is the tetrasodium salt of said acid.
 5. A process for the preparation of alkali metal salts of 2-(N, N-di-(carboxymethyl) )amino-3-sulfopropionic acid which comprises reacting an alkali metal salt of 2-amino-3-sulfopropionic acid with an alkali metal salt of a monohaloacetic acid in an alkaline aqueous system at a mildly elevated temperature and at a pH not in excess of
 10. 6. The process of claim 5 wHerein the alkali metal content of said system is sodium or potassium, or both, and the halogen of the haloacetic acid is chlorine, bromine or iodine.
 7. The process of claim 5 wherein the alkali metal content of said system is sodium, the halogen of the haloacetic acid is chlorine, and the temperature is kept in the vicinity of about 70*-75 * C. 